1. Field of the Invention
The present invention relates to a digital broadcasting system, and more particularly, to a digital broadcasting system and a method for operating the system which can improve equalization performance by judging channel states of an inputted signal by using a field sync. The present application is based on Korean Patent Application No. 2003-7591 and U.S. Provisional Application No. 60/430,086, which are incorporated herein byreference.
2. Description of the Prior Art
As generally known in the art, as means of communication, computers and broadcasting have been integrated and become multimedia, and countries all over the world have turned existing analog broadcasting into digital broadcasting. Particularly, advanced countries such as the USA, Europe and Japan are already providing digital broadcasting in part through satellites. Further, standards for digital broadcasting have been prepared, but such standards vary from country to country.
The FCC (federal communications commission) in the USA has approved a digital TV standard of ATSC (advanced television systems committee) as the next standard for TV broadcasting. In view of this approval, terrestrial broadcasters should abide by standards regarding video/audio compression, transmission structure of packet data, modulation and the transmission system provided by the ATSC standard. However, since standards for video format have not been provided particularly in the ATSC standard, the industry has come to determine them autonomously.
According to the ATSC standard, the MPEG (moving picture experts group)-2 video standard (ISO/IEC IS 13818-2) has been selected as a video compression method. All digital broadcasting all over the world use MPEG-2 as a standard. Further, digital audio compression standard (AC-3) has been selected as an audio compression method, and the MPEG-2 system standard (ISO/IEC IS 13818-1) has been selected as a multiplexing method.
FIG. 1 is a view showing a conventional construction of a data frame in ATSC. Referring to FIG. 1, an ATSC field is composed of 313 continuous segments, and an ATSC field sync is composed of one segment. An ATSC frame is composed of two ATSC fields.
FIG. 2 is a view showing an ATSC field sync. The ATSC field sync comprises a segment sync composed of four symbols, a PN (pseudo noise) sequence composed of 511 symbols, three PN sequences composed of 63 symbols, a transmission mode composed of 24 symbols, 92 symbols reserved and 12 precode symbols.
In a typical construction of an ATSC frame shown in FIG. 1 and FIG. 2, operation modes of a conventional equalizer are a training mode operated by means of LMS algorithm using a PN sequence from among the field sync inputted by a field unit and a blind mode operated by means of a blind algorithm using other data, etc.
Typically, performance of an equalizer, such as a convergence speed and convergence level, are greatly affected by the construction of the equalizer, the blind algorithm used and step sizes. Accordingly, the construction of the equalizer, the blind algorithm used, and step sizes, which have an effect on equalization performance, depend on states of static channels and dynamic channels.
However, information for channel states in received signals has not been provided to the equalizer in a conventional digital communication system. Accordingly, since the conventional digital communication system cannot properly cope with the state change of static channels and dynamic channels, the equalization performance is reduced.